Giant Tree-Dwelling, Coconut-Eating Rat Species Discovered

An illustration of the new giant rat species, Uromys vika. Credit: Velizar Simeonovski The Field Museum

Advertisement

On his first trip to the Solomon Islands in 2010 Tyrone Lavery heard rumors about a strange rodent on Vangunu Island. The giant rat, according to locals, lived in the rainforest canopy and could crack open coconuts with its teeth.

Vangunu is situated some 1,000 miles northwest of Australia, at the western end of the 900-plus-island archipelago. The “vika,” as the creature is known, was apparently once familiar enough that it featured in Vangunu children’s songs and nursery rhymes. Scientists had been hearing about the rats from locals since at least the early 1990s, but none of these researchers had ever seen one.

To determine whether the rodent was a new species, all Lavery, a mammalogist at Chicago’s Field Museum, had to do was find one. That proved more difficult than it sounds. “We put out camera traps, placed [mammal] traps in trees, searched hollow trees [and] spotlighted,” he says, referring to a wildlife surveying method that involves using a flashlight to detect light reflecting from animals’ eyes at night. Beyond a single piece of rodent poop, “we hadn't been able to find any sign of it,” he says. “Until now."

Hikuna Judge, a wildlife ranger from the Zaira Conservation Area, happened to be in the right place at the right time when he spotted and captured a large rodent scampering away from a felled tree. Local elders confirmed this creature was indeed the mysterious vika, and after comparing the specimen to other known rats, Lavery verified the species had never been documented scientifically. Lavery and Judge announced their discovery and described the new species Wednesday, in the Journal of Mammalogy. They called it Uromys vika, in honor of its local name.

The odd creature is the first new Solomon Islands rodent to be described in more than 80 years. David Boseto, a Solomons-based ecologist who was not involved in the study, says this feat would likely have been impossible if not for Lavery's work to engage indigenous communities with the research, underlining the importance of incorporating local knowledge into the process of scientific discovery.

Unlike the 200-gram (seven-ounce) common street rat, this critter weighs nearly a kilogram (2.2 pounds), and measures 46 centimeters (18 inches) from nose to tail. It excavates holes in coconuts with its teeth to reach the meat and juice inside. The Vangunu giant rat—the creature's common name—is presumed to live in the tree canopy where it feasts on fruits and nuts, as revealed by analysis of specimen and scat samples. It occupies the ecological role filled by similar-size mammals in other rainforests, such as opossums or small monkeys. Its only natural predators are raptors like the Solomon sea eagle. The rats must also contend with the threat of feral cats, which have the dubious distinction of being the animals that appeared most frequently on Lavery's camera traps.

But humans pose the biggest threat. “Like most islands in the Solomons, over 90 percent of the land is still owned by indigenous people,” Lavery says of Vangunu. The people there live a subsistence lifestyle, growing vegetables in their gardens, fishing from the reefs and hunting in the rainforests. But foreign timber companies have begun enticing local communities with nearly irresistible financial offers in exchange for logging rights. As a result, the tree-dwelling Vangunu giant rat appears completely absent from areas of the island that have been subject to intensive logging.

Nuts chewed by the rat. Credit: Tyrone Lavery The Field Museum

There is good news for the massive rodents, however. The Zaira Conservation Area encompasses three zones within the rainforest. Hunting is only allowed in one zone at a time, giving biodiversity in the hunter-free areas several years to recover before exploitation begins once again. (The rats are not hunted themselves but by rotating the hunting blocks the community ensures that all the rainforest's inhabitants have a chance to recover from the direct and indirect impacts of human activities.) The Zaira community has so far resisted encroachment by logging companies. Therefore, this conservation area is one of the few places on the island where the rat continues to survive. The researchers argue the species should be designated as “critically endangered,” in part because its already small habitat continues to disappear.

If not for Lavery's persistence and Judge’s serendipitous sighting, the vika might have vanished before it had ever been described scientifically. Now Lavery has shifted his species quest to the nearby island of Malaita, where locals tell him of a type of bat they call the monkey-faced bat. “It’s possible it might have already become extinct,” he says. But he's looking for it anyway.

ABOUT THE AUTHOR(S)

Jason G. Goldman

Jason G. Goldman is a science journalist based in Los Angeles. He has written about animal behavior, wildlife biology, conservation, and ecology for Scientific American, Los Angeles magazine, The Washington Post, The Guardian, the BBC, Conservation magazine, and elsewhere. He contributes to Scientific American's "60-Second Science" podcast, and is co-editor of Science Blogging: The Essential Guide (Yale University Press). He enjoys sharing his wildlife knowledge on television and on the radio, and often speaks to the public about wildlife and science communication.

Scientific American is part of Springer Nature, which owns or has commercial relations with thousands of scientific publications (many of them can be found at www.springernature.com/us). Scientific American maintains a strict policy of editorial independence in reporting developments in science to our readers.